Eri is the granddaughter of the Shie Hassaikai's boss. She was also the key source of Kai Chisaki's operation to manufacture a Quirk-Destroying Drug. She has been living at the U.A. dormitories since she was rescued. Eri's Quirk allows her to reverse a living individual's body back to a previous state, allowing her to make her target physically younger, heal injuries, and undo bodily modifications. She has even shown the ability to rewind someone.